Introduction to the Method Steps for Measuring DC Current with a Multimeter
Mechanical Zero Adjustment:
Similar to measuring resistance and voltage, the multimeter needs to be mechanically zeroed before use. The method of mechanical zero adjustment is the same as the mechanical zero adjustment operation for measuring resistance and voltage previously described. It will not be repeated here. Generally, for commonly used multimeters, mechanical zero adjustment is not required every time.
Selecting the Range:
Estimate the magnitude of the DC current to be measured based on the current of the power source in the circuit to be measured. If the magnitude of the current is not clear, first measure with the highest current range (500mA range). Gradually switch to a lower current range until a suitable current range is found (the standard is the same as that for measuring voltage).
Measurement Method:
When using the current range of the multimeter to measure current, the multimeter should be connected in series in the circuit under test. This is because only when connected in series can the current flowing through the ammeter be the same as the current in the measured branch. During measurement, the branch under test should be disconnected, and the red and black probes of the multimeter should be connected in series between the two disconnected points. Special attention should be paid that the ammeter cannot be connected in parallel in the circuit under test, as this is very dangerous and can easily burn out the multimeter. At the same time, pay attention to the polarity of the red and black test leads. The red test lead should be connected to the current inflow end of the circuit under test, and the black test lead should be connected to the current outflow end of the circuit under test (the polarity selection is the same as that for DC voltage).
Correct Use of Scales and Reading:
When the multimeter is used to measure DC current, the scale line on the dial is the same as that for measuring voltage, which is the second scale line (there is an "mA" symbol on the right side of the second scale line). The characteristics of other scales and the reading method are the same as those for measuring voltage.
If the current to be measured is greater than 500mA, the 5A range can be selected. Operation method: Set the transfer switch to the 500mA range, take out the red test lead from the original "+" jack, and insert it into the jack marked 5A at the lower right corner of the multimeter to measure large currents below 5A.
